Core Java : Exception Handling Interview
Questions
There is given a list of exception handling
interview questions with answers. If you know any exception handling interview
question, kindly post it in the comment section.
73) What is Exception Handling?
Exception Handling is a mechanism to handle
runtime errors.It is mainly used to handle checked exceptions.
74) What is difference between Checked Exception
and Unchecked Exception?
1)Checked Exception:
The classes that extend Throwable class except
RuntimeException and Error are known as checked exceptions
e.g.IOException,SQLException etc. Checked exceptions are checked at
compile-time.
2)Unchecked Exception:
The classes that extend RuntimeException are
known as unchecked exceptions e.g. ArithmeticException,NullPointerException
etc. Unchecked exceptions are not checked at compile-time.
75) What is the base class for Error and
Exception?
Throwable.
76) Is it necessary that each try block must
be followed by a catch block?
It is not necessary that each try block must be
followed by a catch block. It should be followed by either a catch block OR a
finally block. And whatever exceptions are likely to be thrown should be
declared in the throws clause of the method.
77) What is finally block?
78) Can finally block be used without catch?
79) Is there any case when finally will not be
executed?
finally block will not be executed if program
exits(either by calling System.exit() or by causing a fatal error that causes
the process to abort).
80)What is difference between throw and
throws?
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throw keyword
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throws keyword
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1)throw is used to explicitly throw an exception.
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throws is used to declare an exception.
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2)checked exceptions can not be propagated with throw only.
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checked exception can be propagated with throws.
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3)throw is followed by an instance.
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throws is followed by class.
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4)throw is used within the method.
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throws is used with the method signature.
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5)You cannot throw multiple exception
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You can declare multiple exception e.g. public void
method()throws IOException,SQLException.
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81) Can an exception be rethrown?
Yes.
82) Can subclass overriding method declare an
exception if parent class method doesn't throw an exception ?
Yes but only unchecked exception not checked.
83) What is exception propagation ?
Forwarding the exception object to the invoking
method is known as exception propagation.
There is given a list of string handling
interview questions with short and pointed answers. If you know any string
handling interview question, kindly post it in the comment section.
84) What is the meaning of immutable in terms
of String?
The simple meaning of immutable is unmodifiable
or unchangeable. Once string object has been created, its value can't be
changed.
85) Why string objects are immutable in java?
Because java uses the concept of string literal.
Suppose there are 5 reference variables,all referes to one object
"sachin".If one reference variable changes the value of the object,
it will be affected to all the reference variables. That is why string objects
are immutable in java.
86) How many ways we can create the string
object?
There are two ways to create the string object,
by string literal and by new keyword.
87) How many objects will be created in the
following code?
1. String s1="Welcome";
2. String s2="Welcome";
3. String s3="Welcome";
Only one object.
88) Why java uses the concept of string
literal?
To make Java more memory efficient (because no
new objects are created if it exists already in string constant pool).
89)How many objects will be created in the
following code?
1. String s = new String("Welcome");
Two objects, one in string constant pool and
other in non-pool(heap).
90) What is the basic difference between
string and stringbuffer object?
String is an immutable object. StringBuffer is a
mutable object.
91) What is the difference between
StringBuffer and StringBuilder ?
StringBuffer is synchronized whereas
StringBuilder is not synchronized.
92) How can we create immutable class in java
?
We can create immutable class as the String
class by defining final class and
93) What is the purpose of toString() method
in java ?
The toString() method returns the string
representation of any object. If you print any object, java compiler internally
invokes the toString() method on the object. So overriding the toString()
method, returns the desired output, it can be the state of an object etc.
depends on your implementation.
Core Java : Nested classes and Interfaces
Interview Questions
94)What is nested class?
A class which is declared inside another class
is known as nested class. There are 4 types of nested class member inner class,
local inner class, annonymous inner class and static nested class.
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